Matic spent two years at the club, after Mourinho had left for Inter, but struggled to break into the first team and was subsequently sold to Benfica by Carlo Ancelotti as a makeweight in the deal that saw David Luiz arrive at Chelsea.
Mourinho brought the Serbia international back from Benfica and, ahead of his likely return from suspension against Paris Saint-Germain on Wednesday, the Chelsea boss maintains he would always have kept Matic.
"If I had been here - left-footed player, 1.95m tall - a midfield player like that would never, never leave," he told reporters.
"The club had Matic here but he left and two players came. I don't think it's fair to be critical.
"At that age it is good for the 'father' club to be protected, because sometimes the evolution of these players is good and sometimes bad.
"It is important to keep control of the situation. So when you have a player you can loan and even sell him but you still have ways of being in control.
"Chelsea were brave in bringing him back. We wanted a midfield player, we had three or four on the table, but the best one was a player that I don't say Chelsea lost, but a player that was involved in a deal.
"So Chelsea were brave to say if we are sure that he is the right one, no criticism will be stronger than that."
Chelsea have drawn praise in recent seasons for their business dealings, with the likes of Fernando Torres, Luiz and Andre Schurrle sold for big fees and Diego Costa, Matic and Juan Cuadrado arriving at Stamford Bridge.
"Probably in the future if Chelsea does business with a young player, they will keep control," Mourinho added.
"But they had so many managers in those years it was difficult to have a philosophy.
"For one manager Matic would be the right profile of player, for another it is Matic 'you can let him go because I don't like him'.
"To have a philosophy is much easier for the board."
